Interest in fuel cell batteries as power sources for portable electronic devices has grown. A fuel cell is an electrochemical cell that uses materials from outside the cell as the active materials for the positive and negative electrodes. Because a fuel cell does not have to contain all of the active materials used to generate electricity, the fuel cell can be made with a small volume relative to the amount of electrical energy produced compared to other types of batteries.
Fuel cells can be categorized according to the types of materials used in the positive electrode (cathode) and negative electrode (anode) reactions. One category of fuel cell is a hydrogen fuel cell using hydrogen as the negative electrode active material and oxygen as the positive electrode active material. When such a fuel cell is discharged, hydrogen is oxidized at the negative electrode to produce hydrogen ions and electrons. The hydrogen ions pass through an electrically nonconductive, ion permeable separator and the electrons pass through an external circuit to the positive electrode, where oxygen is reduced.
A fuel cell system can include a fuel cell battery, including one or more fuel cells and a hydrogen source. In order to produce a sufficient amount of power, a plurality of individual cells may be stacked in series to form a fuel cell stack. Generally, intimate contact must be maintained throughout the stack of individual fuel cells as the fuel cells hydrate and dehydrate to expand and contract during usage. Compression systems are typically employed to apply a compressive load to the stack which typically includes springs between the end plates which are connected with tension members via bolts or threaded rods.
It is desirable to provide for a compression system for a fuel cell stack that has one or more of the following features: provides uniform compression of the fuel cell stack, is simple and easy to manufacture and assemble, and has long-term durability and easy and economic manufacturing.